Under feudalism, where knowledge was divine, there was very tight consensus, managed by the church or religious authority.

Under capitalism / ProjectMan, there was, theoretically a free-market in ideas, supported by literal free-markets in books, journals and PrintMedia.

However, even here, there were forces of consolidation : most respectable knowledge was produced by state sanctioned universities and those educated and qualified by them. And distributed by an oligopoly / oligopsony of serious publishing companies.

Fragmentation was still possible, compare the conventional wisdom of the social sciences with economics etc. But there were strong tendencies towards consolidation.

Now, with the NationStateUnderAttack, NewMediaVsAcademia and the internet, the tendencies towards consolidation are ever weakened. Everyone is developing their own world-view and repository of beliefs, dependent on their own personal network of influences. Religion is resurgent against rational humanism, pseudo-science and extreme political positions get new exposure. WikiPedia is ever more disputed. ConspiracyTheory abounds.

To say the internet is full of nonsense is over-simplistic. It's daily evidence that consensus has broken down. In its place is NetworkEpistemology.

And how do we make our decision? Appeal to those who the state or the media annoint experts? Agree with friends in our social network? Do a solitary critical analysis?

I wonder if there's a connection with MarketsAsBonfiresOfReason? For topics which are politically contentious : GunControl, IntelligentDesign etc. might the free-market of online communication end up with a ZeroSumGame. Each person desperately trying to "win" the argument (increasingly to avoid the CognitiveDissonance of being wrong ie. WhenProphecyFails) picks more holes in, and spreads more FUD about the opponent (often resorting to critiques of methodology or easily revisably trivial details rather than the overall spirit of the thing.) Essentially, the criticism space becomes polluted with a crud of misunderstandings and half-understood critical minutae. (See also : SwiftBoating)